There weren't enough life boats for everyone on board. The crew wasn't prepared for a full-scale evacuation. And a nearby ship that might have sailed to the rescue misread distress flares.
That was the case 100 years ago, on April 15, 1912, when the Titanic struck an iceberg and sank in the North Atlantic on its maiden voyage, killing 1,517 people aboard.
It was one of the deadliest maritime accidents ever, and led to significant improvements in safety rules aimed at preventing similar calamities. Today's cruise ships are far better equipped to cope with emergencies. Disasters at sea are rare.
Still, the question lingers: Could it happen again?
"The answer is yes, because it just did," said Daniel Allen Butler, a historian and author of "Unsinkable: The Full Story of RMS Titanic." He referred to the Costa Concordia accident in January.
"If the Costa Concordia had been, say, off the coast of Alaska rather than off the coast of Italy, it would have been a disaster of enormous proportions," said Butler.
The location difference is huge. The Titanic sank 370 miles off the coast of Newfoundland in an open ocean that was 12,000-feet deep. Most of the people died from hypothermia in the 28-degree water after the ship went down.
The Costa Concordia struck a rock outcropping just off a Tuscan island that tore a 165-foot hole in its port hull, causing it to go aground in shallow water and eventually tip to her starboard side. Yet 30 people died during a confusing, six-hour long evacuation process.
Unlike the Titanic, there were sufficient lifeboats. That was one of the rule changes that evolved from the Titanic’s sinking – a lifeboat seat for everyone on an ocean liner. The Titanic had only 20 lifeboats, with between 65 and 40 seats each, or enough for just a third of the ship’s capacity and half the number of people on its doomed voyage.